In the conventional fluid bearing cylinder device with its particular structure as shown in FIG. 1, a fixed shaft 2 is pressed in and secured in place at the central portion of a lower cylinder 1, a sleeve 3 is rotatably mounted on the fixed shaft 2, a thrust bearing seat 4 is screwed on the top of the fixed shaft 2 and a thrust bearing 5 is screwed on the upper end of the sleeve 3. Herringbone shaped patterns of grooves 6A and 6B are formed on the fixed shaft 2 and a spiral groove 7 is formed on the lower surface of the thrust bearing 5 by etching, etc. The space inside the bearing chamber formed between the shaft 2 and the sleeve 3 contains lubricant 8, which is oil or grease, etc., thereby comprising a dynamic pressure type fluid bearing. A rotary magnetic head 10 is mounted on an upper cylinder 9, which is mounted on the sleeve 3. Also mounted on the sleeve 3 is a disc shape rotary transformer 11 on the rotary side of the rotary head device for transmitting to the stationary side an electrical signal extracted from a magnetic tape, not shown in the drawings, through the magnetic head 10. An armature magnet 13 is supported on an armature magnet case 14 of a motor attached to a lower end of the sleeve 3, which together with the other parts mentioned above comprise a rotary side unit 20. On the other hand, inside the lower cylinder 1 is mounted a disc shape rotary transformer 12 on the stationary side of the rotary head device which receives the aforementioned electric signal. Also inside the lower cylinder 1, there is secured a motor stator 19 consisting of an iron plate 18, a printed substrate 17 and a coil 16. As the motor is energized under this state, the rotary unit 20 begins turning, producing a pressure by a pumping action of the patterns of grooves 6A, 6B and 7; then, the unit is floated up by the rising rigidity of the oil film, thereby enabling rotation of the rotary side unit 20 without making contact with the stationary side unit. Under this condition, the force of the armature magnet 13 to attract the iron plate 18 and the dead weight of the rotary side unit is exerted in the direction of arrow B as shown in FIG. 1, while a force opposing them is produced in the direction of arrow A as shown in this figure by the pumping action of the spiral groove 7. These forces are balanced and, as a result, the rotary side unit is rotated in a stable condition at a specified height.
With such a structure as described above, the rotary transformers 11 and 12 are in a disc shape, resulting in a thick fluid bearing cylinder device as a whole. Moreover, as shown in FIG. 2, when this device is tilted sideways by 90 degrees, the stationary shaft 2 tends to warp, causing a shift in the relative positions between the magnetic head 10 and the magnetic tape 60, thus interfering with normal play back, etc., of a video tape recorder (hereinafter abbreviated to VTR), etc. For a portable VTR, this device was inadequate with respect to its size and performance.